The enhancement of plastic materials through the incorporation of reinforcing materials therein has been recognized. Polyesters, for example, have long been combined with fiberglass in instances where the articles manufactured must be characterized by improved physical properties. While such composites enjoy wide-spread popularity as a consequence of their enhanced performance, they exhibit certain disadvantages that limit their usefulness. For example, relatively high loadings of the reinforcing fibers are required to achieve the improved properties exhibited by such materials. However, due to such high-fiber loadings, and because of the length of the fibers needed to impart a reinforcing effect, processing of the materials is frequently difficult.
There have been many recent attempts, therefore, to incorporate reinforcing molecules in the matrix material, for instance, by physically blending the components of the composite together. In this regard, dispersions of reinforcing rigid-backbone or extended-chain polymers have often been physically combined with random coil polymer matrices. Such composites are normally distinguished by possessing improved tensile strengths, moduli, elongations and heat resistance, compared to fiber-reinforced systems.
The physical blending referred to can be accomplished, for instance, by melt-mixing thermoplastic nylon 66 with reinforcing materials such as poly-p-phenylene terephthalamide, M. Takayanagi et al., J. Macromol Sci.--Physics B17, 591 (1980). Similarly, W. F. Hwang et al., J. Macromol Sci.--Physics 822(2), 231 (1983) have codissolved reinforcing poly(p-phenylenebenzobisthizole) in plastic materials. U.S. Pat. No. 4,377,546 teaches composite materials cast from methane sulfonic acid, while U.S. Pat. No. 4,631,318 discloses a composite formed from poly(p-phenylenebenzobisthizole) and nylon prepared from a solution of methane sulfonic acid. Further, U.S. Pat. No. 4,614,784 suggests a solution of a rigid-backbone-like liquid crystalline polymer in a polymerizable solvent that is subsequently polymerized to yield a polymeric liquid crystalline or isotropic alloy. U.S. Pat. No. 5,068,292 teaches the solution of the precursors to rigid-backbone polymers in the presence of the matrix polymers, polymerization of the materials proceeding thereafter in sequence, or simultaneously.
The above techniques are not without certain difficulties, however, including such things as the need to use strong acids as solvents; troubles experienced in achieving the desired dispersions on a molecular level; limited solubilities of suitable rigid-backbone polymers in polymerizable solvents, and other problems.
Furthermore, although molecular composites can be prepared by the physical blending of components, phase separations are frequently encountered, especially with increasing levels of the rigid-backbone molecules, or during the processing of the blends. For example, there is often a tendency of the several components to arrange themselves into separate phases, defeating the desired reinforcement objective. Such results arise, for instance, as a consequence of the limited compatibility of the rigid-backbone components with the random coil polymers, caused by the relatively low entropy of mixing.
In view of the preceding, therefore, it is a first objective of this invention to provide improved reinforced polymeric composites.
A second objective of this invention is to provide molecular composites by chemically bonding rigid-backbone reinforcing molecules with random coil matrix polymers.
Another aspect of this invention is to provide reinforcing rigid-backbone polyimides useful for reinforcing polycaprolactam.
An additional aspect of this invention is to prevent reinforcing molecules from phase separation in nylon 6 polymers with which they are combined.
Yet an additional aspect of this invention is to provide molecularly reinforced polycaprolactams that show improved characteristics such as superior chemical resistance, better thermal stability, and enhanced mechanical properties.
A still additional aspect of this invention is to provide chemically bonded polyimide/nylon 6 molecules that overcome the inherent deficiencies of nylon 6 relative to other materials of comparable cost, for example, their low heat deflection temperature, poor dimensional stability, and reduced physical impact strength.
A further aspect of this invention is to provide a rigid polyimide polymer chain grafted from or blocked to, or with a nylon-6 polymer chain.
Another aspect of this invention is to provide polymer compatibilizing agents.
Still another aspect of this invention is to provide synthetic fibers formed from molecular composites.